The present invention generally relates to a radiant burner and, more particularly, to a refractory skeleton for use in forming the radiant burner.
An in-house heating device designed to heat a room by combustion of fuel, such as a gas stove or an oil stove, is known as equipped with a refractory skeleton for facilitating the combustion of fuel and/or radiating infrared rays. This refractory skeleton is placed adjacent the burner and adapted to be red-heated by the flame rising from the burner for facilitating the combustion of fuel and/or enhancing the radiation of infrared rays.
A refractory skeleton hitherto used is generally made of ceramics comprising a chamotte of Al.sub.2 O.sub.3 -SiO.sub.2 system and is prepared by sintering the chamotte, after having been molded into a desired shape, at an elevated temperature higher than 1,000.degree. C. The employment of such a high temperature is known as desirable for increasing the physical strength of the resultant skeleton, but has been found resulting in the reduction of the porosity with no air being substantially mixed. Accordingly, it has long been a customary practice to add an expanding agent to the chamotte, or to employ a reduced sintering temperature, to make the resultant skeleton full of pores even though the physical strength thereof may be sacrificed a certain extent. This means that the prior art burner skeleton when heated to a red-hot state, is fragile and is easy to fracture.
In addition, since the chamotte does not exhibit a chemical bonding ability, a honeycomb structure molded from the chamotte has shown that the partition walls separating a multiplicity of parallel closely adjacent channels from each other in the honeycomb structure have a wall thickness of greater than 1 mm, with the consequent porosity being lower than 40%. Therefore, the ceramic skeleton has a relatively large heat capacity, requiring a relatively long time for it to be substantially red-heated subsequent to the start of heating, or sometimes failing to attain a red-hot state.
In view of the foregoing, various attempts have been made to add silica-alumina fibers with a view to increasing the physical strength, or to form a multiplicity of pyramid-shaped or conical projections on the surfaces of the skeleton with a view to enhancing the red-hot state. Even these attempts were found to be unsatisfactory in eliminating the above discussed problems.